Hermione is completely sensible there--and actually, I always think that's interesting because it follows along the line of thinking that she *will* stand up to her friends when it comes to protecting them. Her flickers of conscience with regards to other people (should we tell what we know about Montague if it will help to cure him?) are much more easily squashed. But maybe if she was surrounded by people she had more in common with than having a cause she might have thought about things differently. I mean, with the Firebolt she still is having to defend her actions by saying she was trying to protect Harry. I think if I were in that situation I'd have far less patience with Harry being angry with me over it. For going behind his back, okay, but it was a perfectly sensible precaution to have it checked out.